Fluid systems utilizing pneumatic and hydraulic fluids have lines, such as pipes and hoses, for carrying the fluid under pressure from a source of fluid pressure to a desired location, such as the fluid motor, fluid cylinder, and the like. Releasable couplers having check valves are used with the lines to provide means to disconnect sections of the fluid systems with a minimum loss of fluid. The couplers are provided with one-way or check valves to prevent drainage of the fluid from the disconnected lines and contamination of the fluid therein. The check valves maintain the fluid under pressure in the valve assemblies and lines. This fluid pressure must be relieved before the lines can be connected to the couplers. This is accomplished by moving the check valves to open positions and allowing a limited amount of fluid to escape. The check valves are moved to open positions by forcing the valves into engagement with a fixed object. The most convenient object is a tractor transmission housing, tire, or frame of the implement. The striking of the check valve against a hard rough surface to break the hydraulic pressure and move the check valve to the open position can damage the outer surface of the check valve and thereby reduce the life of the coupler, as well as the effective pressurization of the hydraulic system. The continued abuse of the check valve will permanently mar its outer surface and cause the check valve to leak hydraulic fluid when in the closed position. The escaping fluid is discharged as a spray into the environment. The spray is not controlled so that it can contaminate the fixed object and the operator.